1. Field of the Invention
This invention relates to a braking system for vehicle, and more particularly to a braking system for vehicle in which the transmission of the pulsating pressure from the brake circuit to the fluid-pressure generating source or master cylinder is limited.
2. Description of the Prior Art
The U.S. Pat. No. 5,020,864 discloses the braking system for a vehicle which comprises a brake fluid pressure generating source; a brake-applying apparatus for braking a wheel or wheels with the brake fluid pressure supplied from said brake fluid pressure generating source; a pulsating-pressure absorbing apparatus arranged between said brake fluid pressure generating source and said brake-applying apparatus; and throttling means arranged in said pulsating-pressure absorbing apparatus, for limiting the brake fluid flowing from the side of said brake-applying apparatus towards said brake fluid pressure generating source, wherein said pulsating-pressure absorbing apparatus further comprises a main body, a plunger slidably fitted through a hole of said main body and being arranged between the inlet and outlet of said main body and further being movable in response to the brake fluid pressure difference between both sides of said plunger, a poppet-type valve body arranged in an axial hole of said plunger and in the inside wall of said plunger, a spherical head portion of said valve body being contactable with said valve seat, a rod portion of said valve body passing through a narrow end portion of said axial hole and said throttle means being formed as a cut off groove in said spherical head portion of the valve body, wherein when said plunger is located at the first side of said outlet, said spherical head portion of the valve body contacts with said valve seat and said cut-out groove functions as a throttle between said spherical head portion of the valve body and said valve seat, and wherein when said plunger is located at the second side of said inlet, said spherical head portion of the valve body is separated from said valve seat.
In the above-described braking system, the plunger is urged towards the outlet side by a spring, and it is located at such a position that brake fluid is returned through the throttling means into the master cylinder (brake fluid pressure generating source) in the lower pressure range. Accordingly, the braking force is slowly decreased in the lower pressure range. It requires much time, and so the responsibility is bad.
In the traction control system, some pressurized fluid of the fluid pressure pump is supplied to the brake-applying apparatus for the driven wheel, so as to prevent slip of the driven wheel on the starting of the vehicle and acceleration thereof. When the brake fluid is slowly returned to the master cylinder side for control cannot be smoothly effected.